We have a new hunting age in Michigan this year, 10 to bow hunt deer!! I will be in this same situation next year with my son, and went through it last year with my daughter.
I dont like to say this because this is not how I like to hunt.
Take them out and let them hunt, mentor them, and get them the best equiptment you can that will increase there chance of a clean kill. The key is to get them interested and let them learn the sport. Let them know that there is a good possibility that they could loose the deer and go from there.
Should it not do the job... Owell.... it is the experience and time spent you child, and they will learn from it either way. They will learn your ethics in time, just make it the best experience you can.